Hemianopsia, or as it is sometimes also referred to "hemianopia", is a pathological condition which takes place entirely in the brain and optical nerve tract. It is caused by stroke, brain tumor, lesions, or other damage to the brain. It results in the loss of half of the field of vision. The condition is generally a homonymous condition which affects both eyes. One refers to a macular split when the hemianopsia goes right down the center of the visual field. The macula is the central portion of the retina.
The area of visual defect, or the one in which no vision is available, is referred to as the scotoma. Depending on the size of the scotoma peripheral or side vision is very substantially reduced whereby the patient cannot see anything in the area of the scotoma without turning his eyes or head.
Hemianopsia usually affects the field of vision in both near and far vision. Devices are known for correcting vision of patients suffering from homonymous hemianopsia, usually by a corrective device containing prisms and/or mirrors, which extends lateral vision. U.S. Pat. Nos. 4,155,633; 4,493,538, and 4,733,958 and the hemianoptic spectacles reviewed in Duke Elder et al., Ophthalmic Optics and Refraction, vol. V., 1970, pp. 704-705, relate to device of this kind.
A major problem in hemianopsia is that it is not perceived by the patient. It does not manifest itself to the patient as a big black spot in the midst of a good field of vision. Therefore, the major problem continues to be the need to remind the patient of the condition and to inculcate habits to respond to nonphysical, but purely mental, memorized stimuli. None of the devices of the prior art provide this kind of training.